Both moves ended up being unnecessary as Boston didn't need the cap space or roster spot as it ended up.
We needed to dump Baynes to sign Kemba.
Not as worked out by doing the double sign and trade with Rozier. Now maybe we don't get to that point without the cap space, or maybe we still do.
Edit: And here's the thing, Boston could have dumped Baynes after the draft if it still needed to. There was no need for urgency at the draft like that, especially at the expense of just dumping a 1st round pick. He did the same thing this year. Just dumped a 1st round pick because he didn't move it before the draft and was left in a situation where he had too many picks. If he would have gotten a future 1st, the trade this year would have been different, but dumping a 1st for two future 2nd's because you had too many picks is just bad asset management.
Baynes wasn't a pure salary dump last year, it was part of a deal to move a first rounder from last year to this year.
This year's draft was weak. Expecting to get a future first for the least valuable first rounder in the draft (one that, due to the guaranteed salaries, is considered less valuable than early second rounders) is too much in most cases.
Look at it this way: if Danny had the #31 pick instead, would you he expected him to turn it into a future first, or think 2 future seconds made sense? Because that pick is generally considered more valuable, but because it isn't a first rounder it doesn't have the same knee jerk "we can't trade a first for second rounders" reaction